1. Field of the Invention
The invention relates to domestic electrical appliances, such as mincers, which have a rotating tool, such as a cutting blade, mounted on the top end of a vertical motor-driven shaft by means of a detachable coupling device comprising a driving element rigidly fastened to the shaft and engageable in a sleeve rigidly fastened to the tool.
2. Description of the Prior Art
In one such kind of appliance as described in U.S. Pat. No. 3,493,022, J. Mantelet, the driving element is provided on the exterior thereof with at least one helical driving spline which winds from bottom to top of the element in the direction of rotation of the driving means and has its active surface facing downwards, while in complementary manner the sleeve carries on the interior thereof at least one helical groove which winds from bottom to top in the aforesaid direction of rotation, but which has its active surface facing upwards. A coupling device of this kind provides in particular the advantage of ensuring that the tool carrier sleeve will be correctly coupled to the driving element as soon as the motor is started up, since the rotation of the shaft of the motor causes the driving spline carried by the drivilng element to engage spontaneously with the complementary groove in the sleeve.
Nevertheless, in certain cases it occurs that the tool continues to turn through the effect of inertia when the motor is abruptly stopped, and then escapes from its driving means, with the consequent risk of causing damage.
It is an object of the present invention to eliminate or greatly reduce this risk of the release of the tool.